From the Pilot Credentials website:

Candidates for jobs involving handling or access to U.S. mail cannot be considered for employment if they have resided outside the U.S., Guam or Puerto Rico for more than (6) six months during the last (5) years prior to today's date, other than the following verifiable exceptions: active duty in the U.S. Uniformed Service; trailing spouse or dependent of someone working for the U.S. government (military or civilian); missionary; student attending school in a foreign country; Peace Corps participant; employee of a U.S. based employer/company or other extraordinary circumstances.

Maybe you can convince them of your extraordinary circumstance